Because every transaction is private, Monero cannot be traced. This makes it a true, @fungible currency. Merchants and individuals accepting Monero do not need to worry about blacklisted or tainted coins.
Unlike selectively transparent alternatives (e.g. Zcash), Monero is the only major cryptocurrency where every user is anonymous by default. The sender, receiver, and amount of every single transaction are hidden through the use of three important technologies: @Stealth-Addresses, @Ring-Signatures, and @RingCT.